1. Field of the Invention
This invention relates to vascular balloon catheters which may be used for percutaneous transluminal angioplasty procedures, or alternatively may be used to position and expand a reinforcing stent within a blood vessel. In particular, this invention is especially adapted to treatment of small diameter blood vessels within the brain and may, for example, be used to temporarily occlude a blood vessel to evaluate the results of the occlusion prior to placing a permanent occlusion device within the vessel.
2. Description of the Prior Art
Medical catheters exist for a wide variety of purposes, including diagnostic procedures and interventional therapy, such as drug delivery, drainage, and perfusion. Catheters for each of these purposes may be introduced to numerous target sites within a patient""s body by guiding the catheter through the vascular system. A wide variety of specific catheter designs have been proposed for such different uses.
Of particular interest to the present invention, small diameter tubular access catheters are presently being used for diagnostic and interventional therapy techniques for vessels within the brain, such as the imaging and treatment of aneurysms, tumors, arteriovenous malformations, and fistulas. Such techniques place a number of requirements on the catheters that are to be employed. The primary requirement is size. The blood vessels in the brain are frequently as small as several millimeters, or less, requiring that catheters have an outside diameter as small as one French (0.33 millimeters). In addition to small size, the brain vasculature is highly tortuous, requiring that catheters used in vessels of the brain be very flexible, particularly at their distal ends, to pass through the regions of tortuosity. Additionally, the blood vessels of the brain are relatively fragile, so it is desirable that the catheters have a soft, non-traumatic exterior to prevent injury.
Balloon catheters are typically formed by bonding an inflatable balloon to a catheter body. Typically, the inflatable balloon is stiff, or non-compliant, and must be properly sized to avoid damaging the fragile blood vessels. The inflatable balloon section is usually thermally or chemically similar to the catheter body, allowing the bond to be formed using adhesive or thermal means. When the balloon is inflated, the construction of the non-compliant balloon causes most of the force to be applied to the inflatable section of the balloon rather than on the bond between the balloon and catheter body. On the other hand, balloons made of compliant materials reduce the need for precise sizing of the balloon. However, due to the chemical differences, adhesives do not form strong bonds between compliant materials, like silicone, and typical catheter-body materials, like polyurethane. When a compliant balloon is inflated, the force on the bond between the compliant balloon and catheter body causes the balloon to peel away from the catheter body. Eventually, the bond fails.
U.S. Pat. No. 4,850,348 to Pell et al., discloses an endotracheal tube with a cuff secured to the outer surface of the tube. The cuff is inflated by means of a pilot balloon connected to the cuff by an external tube and internal passage in the wall of the tube. The distal end of the cuff has an annular end that is secured in contact with the tube and faces in the direction of the proximal end of the tube. Thus, the annular end and distal radiopaque band are located interior to the cuff body.
U.S. Pat. No. 5,876,376 to Schwab et al., discloses a catheter balloon bonding stopper in which the stopper is used to prevent adhesive from wicking between the catheter body and the balloon tail into the balloon. U.S. Pat. No. 5,643,209 to Fugoso et al., discloses an adhesive bond between the inner surface of the distal tail of the balloon and the outer surface of the guidewire shaft. The adhesive bond continues as a filler beyond the balloon distal tip and gradually tapers distally to the same diameter as the outer diameter of the guidewire shaft step down portion.
U.S. Pat. No. 5,700,243 to Narcisco, Jr., discloses radiopaque bands used to crimp a balloon on a catheter shaft. U.S. Pat. No. 3,866,599 to Johnson, discloses clamping rings employed to attach an expandable sleeve to the body of a catheter.
In accordance with the present invention, there is provided a balloon catheter having a balloon and a catheter body formed of dissimilar polymeric materials. The balloon catheter includes a catheter body that includes an outer tubular member and an inner tubular member that is coaxial with and runs longitudinally through the outer tubular member and extends distally beyond the distal end of the outer tubular member, and an inflatable balloon. The outer and inner tubular members are formed from a first polymeric material. The inflatable balloon is formed from a second polymeric material, which differs from the first polymeric material. The inflatable balloon is attached at the proximal end by a first layer of adhesive material interposed between the inner surface of the proximal portion of the balloon and the distal end of the outer tubular member to bond the inner surface of the proximal portion of the balloon to the distal end of the outer tubular member. This bond is reinforced by a first retaining ring positioned over and crimped tightly around the proximal portion of the balloon. Similarly, the inflatable balloon is attached at the distal end by a second layer of adhesive material interposed between the inner surface of the distal portion of the balloon and the distal end of the inner tubular member. This bond is reinforced by a second retaining ring positioned over and crimped tightly around the distal portion of the balloon. In addition, the balloon catheter includes a coupling member, having a lumen extending therethrough, mounted on the proximal end of the outer tubular member and the lumen of the coupling member communicating with the lumen between the outer tubular member and the inner tubular member so that fluid may be injected into the lumen of the coupling member to inflate the balloon.
In accordance with another aspect of the present invention, the first polymeric material is formed of polyurethane, the second polymeric material is formed of silicone, and the first and second layers of adhesive materials are formed of silicone.
In accordance with another aspect of the present invention, there is provided a balloon catheter having a balloon and a catheter body. The balloon catheter includes a catheter body that includes an outer tubular member and an inner tubular member that is coaxial with and runs longitudinally through the outer tubular member and extends distally beyond the distal end of the outer tubular member, and an inflatable balloon. The inflatable balloon is attached at the proximal end by a first layer of adhesive material interposed between the inner surface of the proximal portion of the balloon and the distal end of the outer tubular member to bond the inner surface of the proximal portion of the balloon to the distal end of the outer tubular member. This bond is reinforced by a first retaining ring positioned over and crimped tightly around the proximal portion of the balloon. Similarly, the inflatable balloon is attached at the distal end by a second layer of adhesive material interposed between the inner surface of the distal portion of the balloon and the distal end of the inner tubular member. This bond is reinforced by a second retaining ring positioned over and crimped tightly around the distal portion of the balloon. In addition, the balloon catheter includes a coupling member, having a lumen extending therethrough, mounted on the proximal end of the outer tubular member and the lumen of the coupling member communicating with the lumen between the outer tubular member and the inner tubular member so that fluid may be injected into the lumen of the coupling member to inflate the balloon.
In accordance with another aspect of the present invention, the first and second retaining rings are formed of a radiopaque material and serve as radiopaque marker bands for positioning the proximal and distal ends of the balloon, respectively. Preferably, the radiopaque marker bands are formed of a biocompatible metallic substance such as gold.
In accordance with yet another aspect of the present invention, the balloon catheter may include proximal and distal retaining ring sleeves. The proximal retaining ring sleeve overlaps the proximal end of the first retaining ring by at least half of the length of the first retaining ring and is heat fused to the outer tubular member and the first retaining ring. The distal retaining ring sleeve is positioned distally adjacent to the second retaining ring and is heat fused to the inner tubular member. The proximal and distal retaining ring sleeves serve to prevent the first and second retaining rings, respectively, from moving along the length of the outer or inner tubular member. Preferably, the proximal retaining ring sleeve is formed of nylon and the distal retaining ring sleeve is formed of polyurethane.
In accordance with still another aspect of the present invention, there is presented a method of manufacturing a balloon catheter that includes an outer tubular member, an inner tubular member, and an inflatable balloon. The method includes the steps of applying a first layer of adhesive material to the distal end of the outer tubular member, inserting the proximal portion of the balloon over the section of the outer tubular member covered by the first layer of adhesive material such that the balloon and the outer tubular member are coaxially oriented, positioning a first retaining ring over the proximal portion of the balloon, crimping a first retaining ring onto the proximal portion of the balloon, inserting the inner tubular member inside the balloon, positioning a second retaining ring over the balloon, applying a second layer of adhesive material onto the distal end of the inner tubular member at a location beneath the distal portion of the balloon, and crimping the second retaining ring onto the distal portion of the balloon.
In accordance with still another aspect of the present invention, there is presented a method of manufacturing a balloon catheter that includes an outer tubular member, an inner tubular member, and an inflatable balloon is presented. The method includes the steps of applying a first layer of adhesive material to the distal end of the outer tubular member, inserting the proximal portion of the balloon over a portion of the outer tubular member covered by the first layer of adhesive material such that the balloon and outer tubular member are coaxially oriented, positioning the first retaining ring over the proximal portion of the balloon, crimping the first retaining ring onto the proximal portion of the balloon, positioning a proximal retaining ring sleeve over at least a half of the first retaining ring and extending over a proximal portion of the first retaining ring, heat fusing the proximal retaining ring sleeve to the outer tubular member and the first retaining ring, inserting the inner tubular member inside the balloon, positioning the second retaining ring over the balloon, applying a second layer of adhesive material onto the distal end of the inner tubular member at a location beneath the distal portion of the balloon, crimping the second retaining ring onto the distal portion of the balloon, positioning a distal retaining ring sleeve distally adjacent to the second retaining ring, and heat fusing the distal retaining ring sleeve to the inner tubular member.
In accordance with still another aspect of the present invention, the method of manufacturing the balloon catheter further includes the step of tapering at least a portion of the distal end of the outer tubular member prior to applying the first layer of adhesive material over the portion of the distal end that is tapered.